seismogramme

Seismogramme, or seismogram in English, is the record of ground motion produced by a seismograph as a function of time. It is generated by a seismometer, an instrument that senses tiny displacements, velocities, or accelerations of the Earth's surface and converts them into an electrical signal.

Modern seismometers measure motion along three orthogonal components: vertical, north-south, and east-west. The signal is recorded on a recording medium, historically a rotating drum with handwriting or ink traces, now a digital waveform data stream that can be displayed as a seismogram on a screen or stored for analysis. The instrument response, filtering, and baseline drift must be understood to interpret the trace correctly.

On a seismogram, waves from an earthquake arrive in a characteristic sequence: P-waves (primary, compressional) first, S-waves (secondary, shear) next, followed by surface waves. The relative arrival times and amplitudes provide information about the distance to the source and its mechanism. Using data from multiple stations allows triangulation to locate the epicenter and estimate depth and magnitude.

Historically, seismographs were developed in the late 19th and early 20th centuries by pioneers such as John Milne, James Ewing and Harry Fielding Reid. Today, worldwide networks of digital sensors provide real-time monitoring for science, public safety, and engineering, along with archival records that support research into Earth structure and seismic hazards.